One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,5)(6,8)(10,17)(11,22)(12,28)(13,30)(14,15)(18,33)(19,20)(21,31)(24,40)(26,27)(34,38)(35,37) involution — undirected(1,2)(3,6)(4,5)(7,8)(9,10,14,17,16,21,15,31)(11,23,26,33,27,39,22,18)(12,29,13,20,30,32,28,19)(24,35,25,38,40,34,36,37)(2,5)(6,7)(9,11,15,22,16,27,14,26)(10,18,17,23,21,33,31,39)(12,24,28,36,30,40,13,25)(19,34,29,37,20,35,32,38)(1,3,4,8)(2,6,5,7)(9,12,15,28,16,30,14,13)(10,19,17,29,21,20,31,32)(11,24,22,36,27,40,26,25)(18,34,23,37,33,35,39,38)(9,13,15,12,16,28,14,30)(10,20,31,29,21,19,17,32)(11,25,22,24,27,36,26,40)(18,35,39,37,33,34,23,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.